IGCTs are semiconductor switching devices that, for example, are used in inverters and other high power electronics devices due to their fast switching behaviour and their low switching losses. An IGCT in the conducting state may be switched off by applying a voltage to the gate of the IGCT. After that, a current between the anode and the cathode is blocked, and the IGCT remains in the blocked state until a negative voltage is applied to the gate again.
Usually, a gate unit is used to control the switching and for example to control the gate voltage of the IGCT. In a known gate unit, the available gate voltage is limited by the gate-commuted thyristor (GCT) technology, for example by the avalanche or breakdown voltage of the diode between the gate and the cathode. For example, the breakdown voltage may be about 24 V and the gate unit may apply a constant voltage of 20 V during switch-off.
In order to improve turn-off switching, during static conditions, one could increase the voltage generated by the gate unit and the breakdown voltage between the gate and the cathode. If in this case, the breakdown voltage is not increased, the gate could be driven into constant avalanche. Increasing the breakdown voltage can be, albeit possible, a monumental change in IGCT technology.
Alternatively, the impedance of the gate circuit may be decreased, which is also possible, but may be subjected to practical limits such as the lateral extension of the silicon wafer, the insulation specifications, cost, etc.